The film takes a bleak look at the war on drugs around the US/Mexico border. Blunt plays Kate Macer, a right-minded FBI agent who is asked to join a special task force by an enigmatic government official (Brolin). Together with a sinister man known only as Alejandro (Del Toro) the team embark on an increasingly dirty mission against a Mexican drug cartel.

The most noticeable thing about Sicario is its reliance on tension over action. One heart-pounding sequence, for example, takes place in a traffic jam as Kate and her fellow agents scan surrounding vehicles for their attackers. We know the violence is coming but where’s it going to come from? Which motorists are a threat and which ones are just innocent bystanders?

Another scene sees Kate positioned at the back of an assault team. There are distant pops of gunfire, slashing sounds and screaming, but none of the horror is immediately visible. Agents fire into dark tunnels as Kate follows behind, sweating and shaking and stepping past dead bodies. There’s a persistent sense that she’s in extreme danger but her enemy doesn’t seem to have a face.

Despite its atmospheric, slow-burn approach there are moments of hard-hitting action in Sicario that make me question why the film wasn’t given an ‘18’ certificate. Buildings explode, thugs are sprayed with bullets and a vehicle smashes into a villain’s lair. It’s thrilling, but it’s also brutal, cruel and very quick. Realism rules as characters’ lives are ended or irreversibly damaged in a split-second.

There are many elements in Sicario that deserve praise – the nightmarish score, the unexpected twists – but the best part of this movie might be Emily Blunt’s acting. She sensitively (and intelligently) portrays an idealistic young woman losing faith in the morality of her profession.

It’s a fascinating exploration of what happens to an individual when they have to sacrifice their principles to win...or simply survive.